Structure of oxide thin film transistor

ABSTRACT

A structure of an oxide thin film transistor includes: an oxide semiconducting layer, an etching stopper layer on the oxide semiconducting layer, and a source and a drain on the etching stopper layer. Two vias are formed in the etching stopper layer. The oxide semiconducting layer includes two recesses formed therein to extend through a skin layer of the oxide semiconducting layer and respectively corresponding to the two vias. The two recesses are respectively connected with and in communication with the two vias. The source and the drain are respectively filled in the two vias and the two recesses connected with the two vias to directly connect to and physically contact the oxide semiconducting layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of co-pending patent application Ser.No. 14/384,447 filed on Sep. 11, 2014, which is a national stage of PCTApplication No. PCT/CN2014/082126, filed on Jul. 14, 2014, claimingforeign priority of Chinese Patent Application No. 201410277587.0, filedon Jun. 19, 2014.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to the field of flat panel displays, andmore particularly to a structure of a thin film transistor backplane.

2. The Related Arts

A thin film transistor (TFT) has been widely utilized as a switchingelement and a driving element in an electronic device. Specifically, dueto the possibility of formation of the thin film transistors on a glasssubstrate or a plastic substrate, they are commonly employed in the flatpanel display field, such as a liquid crystal display (LCD), an organiclight emitting diode (OLED), and etc.

The oxide semiconductor has higher electron mobility (the mobility ofthe oxide semiconductor is >10 cm²/Vs and the mobility of the amorphoussilicon (a-Si) is merely 0.5-0.8 cm²/Vs) and has a simpler manufacturingprocess in comparison with low temperature poly-silicon (LTPS) andhigher compatibility in comparison with an amorphous silicon process.Therefore, it can be applied to the field of liquid crystal displays,organic light emitting displays, flexible displays, and the likes.Because it fits the new generation production lines and the possibleapplications in displays with large, middle and small sizes. The oxidesemiconductor is hot to the research field of the present industrybecause the great opportunity of application development.

The oxide semiconductor has advantages of a higher electron mobility anda simpler manufacturing process. Nevertheless, some drawbacks exist. Thestability is bad and big influence with temperature and humidity exists.The electric property of the oxide semiconductor drifts with time. Theoxide semiconductor requires higher demands for process conditions, suchas the film formation rate, the atmosphere and the temperature of theprocess, control of the temperature, etc. Besides, higher demands arefurther required for the isolation layer, the contact between the oxidesemiconducting layer and the isolation layer, the contact between theoxide semiconducting layer and the metal layer. Restrict demanding theoxide semiconducting layer itself is not enough as regarding an oxidethin film transistor.

Referring to FIG. 1, which is a sectional view diagram of a structure ofa bottom gate type oxide thin film transistor according to prior art, amanufacturing method of the structure of the oxide thin film transistormainly comprises: step 1, providing a substrate (100); step 2, forming agate (200) on the substrate (100); step 3, covering the gate (200) witha gate isolated layer (300); step 4, forming an oxide semiconductinglayer (400) on the gate isolated layer (300); step 5, forming an etchingstopper layer (500) on the oxide semiconducting layer (400); step 6,respectively forming two vias (510, 530) in the etching stopper layer(500) to expose the oxide semiconducting layer (400); step 7, forming asource (610) and a drain (630) on the etching stopper layer (500),wherein the source (610) fills in one via (510) and connects with theoxide semiconducting layer (400) and the drain (630) fills in the othervia (530) and connects with the oxide semiconducting layer (400); step8, forming a protective layer (700) on the source (610) and the drain(630) for covering the source (610) and the drain (630).

In the aforementioned manufacturing method of the oxide thin filmtransistor, the etching stopper layer (500) of step 5 is generallyformed of a SiOx film layer, which is manufactured with TEOS+O2 orSiH4+N2O chemical vapor deposition. However, plasma will affect thesurface property of the oxide semiconducting layer (400) when the filmof the etching stopper layer (500) is formed. For instance, SiH4+N2Ocontains hydrogen which may combines with the oxygen in the oxidesemiconducting layer (400) and leads into increase of the oxygendefects. As a result, the threshold voltage Vth tends to be negative.The oxygen in TEOS+O2 leads into decrease of the oxygen defects in theoxide semiconducting layer (400) and reduces the conductivity of thetrench. Therefore, what contacts with the source (610) and the drain(630) is the damaged surface of the oxide semiconducting layer (400).Ultimately, the electrical property of the oxide thin film transistor isaffected. Referring to FIG. 2, which is a curve diagram of theelectrical property of an oxide thin film transistor according to priorart, the threshold voltage Vth=−5V and subthreshold swing S.S=0.45 whenthe voltage of the drain Vd=10V. The electrical property of the oxidethin film transistor can be worse.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a manufacturingmethod of an oxide thin film transistor. By using the manufacturingmethod, a source and a drain can contact an oxide semiconducting layerwhich is not damaged and remains the original property. The oxide thinfilm transistor formed by the manufacturing method possesses more stableand more excellent electrical property.

Another objective of the present invention is to provide a structure ofoxide thin film transistor which possesses an excellent electricalproperty and improves the quality of the oxide thin film transistor.

To realize the aforesaid objectives, the present invention provides amanufacturing method of an oxide thin film transistor, comprising thefollowing steps:

Step 1, providing a carrier;

Step 2, forming an oxide semiconducting layer on the carrier;

Step 3, forming an etching stopper layer on the oxide semiconductinglayer;

Step 4, forming two vias in the etching stopper layer to expose theoxide semiconducting layer;

Step 5, removing a skin layer of the oxide semiconducting layer in thetwo vias to form two recesses respectively connecting the two vias;

Step 6, forming a source and a drain on the etching stopper layer, andthe source fills one via and the recess connecting therewith to connectto the oxide semiconducting layer, and the drain fills the other via andthe recess connecting therewith to connect to the oxide semiconductinglayer.

The etching stopper layer is formed on the oxide semiconducting layer bychemical vapor deposition. The two vias are formed in the etchingstopper layer by dry etching. The source and the drain are formed on theetching stopper layer by sputtering. The skin layer of the oxidesemiconducting layer in the two vias are removed by dry etching or wetetching.

The etching stopper layer is a SiOx film layer formed with TEOS+O2 orSiH4+N2O chemical vapor deposition.

The carrier comprises a substrate, a gate formed on the substrate and agate isolated layer formed on the substrate and the gate.

The manufacturing method of the oxide thin film transistor furthercomprises Step 7 of performing a post process, and the post processcomprises forming a protective layer on the source and the drain tocover the source and the drain.

The carrier is a substrate.

The manufacturing method of the oxide thin film transistor furthercomprises Step 7 of performing a post process, and the post processcomprises forming a gate isolated layer on the source and the drain, andsputtering a gate on the gate isolated layer.

The present invention further provides a structure of oxide thin filmtransistor, comprising: an oxide semiconducting layer, an etchingstopper layer on the oxide semiconducting layer, and a source and adrain on the etching stopper layer, and two vias are formed in theetching stopper layer, and the oxide semiconducting layer comprises tworecesses respectively corresponding to the two vias and the two recessesrespectively connect with the two vias, and the source fills one via andthe recess connecting therewith to connect to the oxide semiconductinglayer, and the drain fills the other via and the recess connectingtherewith to connect to the oxide semiconducting layer.

The structure of the oxide thin film transistor further comprises asubstrate, a gate on the substrate, a gate isolated layer on thesubstrate and the gate, and a protective layer on the source and thedrain; the oxide semiconducting layer is located on the gate isolatedlayer.

The structure of the oxide thin film transistor further comprises asubstrate, a gate isolated layer on the source and the drain, and a gateon the gate isolated layer; the oxide semiconducting layer is located onthe substrate.

The present invention further provides a structure of an oxide thin filmtransistor, comprising: an oxide semiconducting layer, an etchingstopper layer on the oxide semiconducting layer, and a source and adrain on the etching stopper layer, and two vias are formed in theetching stopper layer, and the oxide semiconducting layer comprises tworecesses respectively corresponding to the two vias and the two recessesrespectively connect with the two vias, and the source fills one via andthe recess connecting therewith to connect to the oxide semiconductinglayer, and the drain fills the other via and the recess connectingtherewith to connect to the oxide semiconducting layer; and thestructure of the oxide thin film transistor further comprises asubstrate, a gate on the substrate, a gate isolated layer on thesubstrate and the gate, and a protective layer on the source and thedrain; the oxide semiconducting layer is located on the gate isolatedlayer.

The benefits of the present invention are: in the manufacturing methodof an oxide thin film transistor according to the present invention, byperforming dry etching or wet etching to a skin layer of an oxidesemiconducting layer exposed in two vias, the skin layer of the oxidesemiconducting layer, which the property is changed due to the damage ofO and H of the plasma when the etching stopper layer is formed isremoved, the source and the drain can contact the oxide semiconductinglayer which is not damaged and remains the original property. The oxidethin film transistor formed by the manufacturing method possesses morestable and more excellent electrical property and the method is simplefor operation. In the structure of the oxide thin film transistoraccording to the present invention, by locating two recesses in theoxide semiconducting layer corresponding to the two vias in the etchingstopper layer, and the two recesses respectively connect with the twovias to allow the source and the drain contact the oxide semiconductinglayer which remains the original property. Accordingly, fine electricalproperty is achievable and the quality of the oxide thin film transistorcan be promoted.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the characteristics and technical aspectof the invention, reference is made to the following detaileddescription of the present invention in combination with the drawings;however, the drawings and the description are provided only forreference and are not intended to limit the invention.

In drawings,

FIG. 1 is a sectional view of a structure of an oxide thin filmtransistor according to prior art;

FIG. 2 is a curve diagram of the electrical property of an oxide thinfilm transistor according to prior art;

FIG. 3 is a flowchart of a manufacturing method of an oxide thin filmtransistor according to a first embodiment of the present invention;

FIG. 4 is a diagram of Step S14 of the manufacturing method of thestructure of the oxide thin film transistor according to the firstembodiment of the present invention;

FIG. 5 is a diagram of Step S15 of the manufacturing method of thestructure of the oxide thin film transistor according to the firstembodiment of the present invention;

FIG. 6 is a diagram of Step S16 of the manufacturing method of thestructure of the oxide thin film transistor according to the firstembodiment of the present invention;

FIG. 7 is a diagram of Step S17 of the manufacturing method of thestructure of the oxide thin film transistor according to the firstembodiment of the present invention and is also a sectional view of astructure of the oxide thin film transistor according to the firstembodiment of the present invention;

FIG. 8 is a curve diagram of the electrical property of an oxide thinfilm transistor according to the present invention;

FIG. 9 is a flowchart of a manufacturing method of an oxide thin filmtransistor according to a second embodiment of the present invention;

FIG. 10 is a diagram of Step S23 of the manufacturing method of theoxide thin film transistor according to the second embodiment of thepresent invention;

FIG. 11 is a diagram of Step S24 of the manufacturing method of theoxide thin film transistor according to the second embodiment of thepresent invention;

FIG. 12 is a diagram of Step S25 of the manufacturing method of theoxide thin film transistor according to the second embodiment of thepresent invention;

FIG. 13 is a diagram of Step S26 of the manufacturing method of theoxide thin film transistor according to the second embodiment of thepresent invention;

FIG. 14 is a diagram of Step S27 of the manufacturing method of theoxide thin film transistor according to the second embodiment of thepresent invention and is also a sectional view of a structure of anoxide thin film transistor according to a second embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will described in detail regardingthe technical matters, structural features, achieved objects, andeffects with reference to the accompanying drawings.

Referring to FIGS. 3-7, which show a manufacturing method of an oxidethin film transistor according to a first embodiment of the presentinvention, the manufacturing method of the first embodiment isapplicable to a bottom gate type thin film transistor. The manufacturingmethod comprises the following steps:

Step S11, providing a carrier.

In the first embodiment, the carrier comprises a substrate 1, a gate 2formed on the substrate 1 and a gate isolated layer 3 formed on thesubstrate 1 and the gate 2. Preferably, the substrate 1 is a glasssubstrate.

Step S12, forming an oxide semiconducting layer 4 on the carrier.

Preferably, a material of the oxide semiconducting layer 4 is indiumgallium zinc oxide semiconducting (IGZO).

Step S13, forming an etching stopper layer 5 on the oxide semiconductinglayer 4.

The etching stopper layer 5 is formed on the oxide semiconducting layer4 by chemical vapor deposition. Furthermore, the etching stopper layer 5is a SiOx film layer formed with TEOS+O2 or SiH4+N2O chemical vapordeposition.

Step S14, forming two vias 51, 53 in the etching stopper layer 5 toexpose the oxide semiconducting layer 4.

In Step S14, the two vias 51, 53 are formed in the etching stopper layer5 by dry etching.

Step S15, removing a skin layer of the oxide semiconducting layer 4 inthe two vias 51, 53 to form two recesses respectively connecting the twovias 51, 53.

In Step S15, the skin layer of the oxide semiconducting layer 4 in thetwo vias 51, 53 are removed by dry etching or wet etching.

In the formation process of the etching stopper layer 5, the skin layerof the oxide semiconducting layer 4 suffers damage caused by O and H ofplasma, resulting in that the property of the skin layer of the oxidesemiconducting layer 4 has been changed. With Step S15, the skin layerof the oxide semiconducting layer 4, which the property is changed dueto the damage of O and H of the plasma is removed. The new formed skinlayer of the oxide semiconducting layer 4 respectively in the recesses41, 43 connecting with the two vias 51, 53 is undamaged and possessesthe original property of the oxide semiconducting layer 4.

Step S16, forming a source 61 and a drain 63 on the etching stopperlayer 5, and the source 61 fills one via 51 and the recess 41 connectingtherewith to connect to the oxide semiconducting layer 4, and the drain63 fills the other via 53 and the recess 43 connecting therewith toconnect to the oxide semiconducting layer 4.

Specifically, the source 61 and the drain 63 are formed on the etchingstopper layer 5 by sputtering.

The source 61 and the drain 63 contact the oxide semiconducting layer 4which remains the original property because the skin layer of the oxidesemiconducting layer 4 in the recesses 41, 43 is not damaged and remainsthe original property.

Step S17, performing a post process, as forming a protective layer 7 onthe source 61 and the drain 63 to cover the source 61 and the drain 63.

Referring to FIG. 8, which is a curve diagram of the electrical propertyof an oxide thin film transistor formed by the aforesaid manufacturingmethod of the oxide thin film transistor, as shown in the figure, thethreshold voltage Vth=0.2V and subthreshold swing S.S=0.13 as thevoltage of the drain Vd=10V. The subthreshold swing S.S becomes smalleras the threshold voltage Vth is near around the 0V. The electricalproperty of the oxide thin film transistor formed by the manufacturingmethod of the structure of the oxide thin film transistor according tothe present invention gets considerable and significant improvement.

Referring to FIGS. 9-14, which show a manufacturing method of an oxidethin film transistor according to a second embodiment of the presentinvention. The manufacturing method of the second embodiment isapplicable to a top gate type thin film transistor. The differences ofthe second embodiment from the first embodiment are provided below:

Step S21, providing a carrier.

In the second embodiment, the carrier is a substrate 1′. The substrate1′ is a transparent substrate. Preferably, the substrate 1′ is a glasssubstrate.

Step S27, performing a post process, as forming a gate isolated layer 3′on the source 61 and the drain 63 and sputtering a gate 2′ on the gateisolated layer 3′.

The remaining steps, Steps S22-S26, which are carried sequentially afterStep S21 and before Step S27 are the same as the counterpart steps,Steps S12-S16, of the first embodiment. Repeated description of thesesteps will not be necessary herein.

On the basis of a manufacturing method of an oxide thin film transistor,the present invention further provides a structure of an oxide thin filmtransistor, which is applicable to a LCD apparatus or a OLED apparatus.

Referring to FIG. 7, which is a sectional view of a structure of anoxide thin film transistor according to a first embodiment of thepresent invention, in the first embodiment, the structure of the oxidethin film transistor, which belongs to a bottom gate type, comprises anoxide semiconducting layer 4, an etching stopper layer 5 on the oxidesemiconducting layer 4, and a source 61 and a drain 63 on the etchingstopper layer 5, wherein two vias 51, 53 are formed in the etchingstopper layer 5; the oxide semiconducting layer 4 comprises two recesses41, 43 respectively corresponding to the two vias 51, 53 and the tworecesses 41, 43 respectively connect with the two vias 51, 53; and thesource 61 fills one via 51 and the recess 41 connecting therewith toconnect to the oxide semiconducting layer 4, and the drain 63 fills theother via 53 and the recess 43 connecting therewith to connect to theoxide semiconducting layer 4. The structure of the oxide thin filmtransistor further comprises a substrate 1, a gate 2 on the substrate 1,a gate isolated layer 3 on the substrate 1 and the gate 2, and aprotective layer 7 on the source 61 and the drain 63. The oxidesemiconducting layer 4 is located on the gate isolated layer 3.Significantly, the two recesses 41, 43 allow the source 61 and the drain63 to contact the oxide semiconducting layer 4, which remains theoriginal property. Therefore, fine electrical property can be achieved.

Referring to FIG. 14, which is a sectional view showing a structure ofan oxide thin film transistor according to a second embodiment of thepresent invention, in the second embodiment, the structure of the oxidethin film transistor belongs to a top gate type. Differences of thesecond embodiment from the first embodiment are that the secondembodiment further comprises a substrate 1′, a gate isolated layer 3′ onthe source and the drain, and a gate 2′ on the gate isolated layer 3′;and the oxide semiconducting layer 4 is located on the substrate 1′.Other structures are the same as those described in the firstembodiment. Repeated explanation will be omitted here.

In conclusion, in the manufacturing method of an oxide thin filmtransistor according to the present invention, by performing dry etchingor wet etching to a skin layer of an oxide semiconducting layer exposedin two vias, the skin layer of the oxide semiconducting layer, of whichthe property is changed due to the damage of O and H of plasma when theetching stopper layer is formed, is removed, and the source and thedrain can contact the oxide semiconducting layer which is not damagedand remains the original property. The oxide thin film transistor formedby the manufacturing method possesses more stable and more excellentelectrical property and the method is simple for operation. In thestructure of the oxide thin film transistor according to the presentinvention, by locating two recesses in the oxide semiconducting layercorresponding to the two vias in the etching stopper layer, and the tworecesses respectively connect with the two vias to allow the source andthe drain contact the oxide semiconducting layer which remains theoriginal property. Accordingly, fine electrical property is achievableand the quality of the oxide thin film transistor can be promoted.

Above are only specific embodiments of the present invention, the scopeof the present invention is not limited to this, and to any persons whoare skilled in the art, change or replacement which is easily derivedshould be covered by the protected scope of the invention. Thus, theprotected scope of the invention should go by the subject claims.

What is claimed is:
 1. A structure of an oxide thin film transistor,comprising: an oxide semiconducting layer, an etching stopper layer onthe oxide semiconducting layer, and a source and a drain on the etchingstopper layer, wherein the oxide semiconducting layer has a bodyexhibiting a predetermined original material property of semiconductionand a skin layer, which is a unitary part of the oxide semiconductinglayer and defines a surface of the oxide semiconducting layer, the skinlayer having a modified material property of semiconduction that isdifferent from the predetermined original material property ofsemiconduction and extends inward from a top face of the oxidesemiconducting layer; two vias are formed in the etching stopper layerand the oxide semiconducting layer comprises two recesses formed in thesurface of the oxide semiconducting layer and extending from the topface of the oxide semiconducting layer to run completely through theskin layer and penetrate into the body of the oxide semiconductinglayer, wherein the two recesses respectively correspond to the two vias,and the two recesses are extended through the skin layer into aninterior of the body so as to expose a part of the body that exhibitsthe predetermined original material property of semiconduction; and thetwo recesses are respectively connected with and in communication withthe two vias, the source being filled in a first one of the vias and afirst one of the recesses that is connected with the first via toconnect to and physically contact the part of the body of the oxidesemiconducting layer that exhibits the predetermined original materialproperty of semiconduction, the drain being filled in a second one ofthe vias and a second one of the recesses connected with the second viato connect to and physically contact the part of the body of the oxidesemiconducting layer that exhibits the predetermined original materialproperty of semiconduction, wherein the source and the drain are bothconnected to the part of the body of the oxide semiconducting layer thatexhibits the predetermined original material property of semiconduction,and the source and the drain are connected to each other by a portion ofthe body of the oxide semiconducting layer that exhibits thepredetermined original material property of semiconduction.
 2. Thestructure of the oxide thin film transistor according to claim 1,further comprising a substrate, a gate on the substrate, a gate isolatedlayer on the substrate and the gate, and a protective layer on thesource and the drain, the oxide semiconducting layer being located onthe gate isolated layer.
 3. The structure of the oxide thin filmtransistor according to claim 1, further comprising a substrate, a gateisolated layer on the source and the drain, and a gate on the gateisolated layer, the oxide semiconducting layer being located on thesubstrate.
 4. A structure of an oxide thin film transistor, comprising:an oxide semiconducting layer, an etching stopper layer on the oxidesemiconducting layer, and a source and a drain on the etching stopperlayer, wherein the oxide semiconducting layer has a body exhibiting apredetermined original material property of semiconduction and a skinlayer, which is a unitary part of the oxide semiconducting layer anddefines a surface of the oxide semiconducting layer, the skin layerhaving a modified material property of semiconduction that is differentfrom the predetermined original material property of semiconduction andextends inward from a top face of the oxide semiconducting layer; twovias are formed in the etching stopper layer and the oxidesemiconducting layer comprises two recesses formed in the surface of theoxide semiconducting layer and extending from the top face of the oxidesemiconducting layer to run completely through the skin layer andpenetrate into the body of the oxide semiconducting layer, wherein thetwo recesses respectively correspond to the two vias, and the tworecesses are extended through the skin layer to penetrate into aninterior of the body so as to expose a part of the interior of the bodythat exhibits the predetermined original material property ofsemiconduction; and the two recesses are respectively connected with andin communication with the two vias, the source being filled in a firstone of the vias and a first one of the recesses that is connected withthe first via to connect to and physically contact the part of the bodyof the oxide semiconducting layer that exhibits the predeterminedoriginal material property of semiconduction, the drain being filled ina second one of the vias and a second one of the recesses connected withthe second via to connect to and physically contact the part of the bodyof the oxide semiconducting layer that exhibits the predeterminedoriginal material property of semiconduction, wherein the source and thedrain are both connected to the part of the body of the oxidesemiconducting layer that exhibits the predetermined original materialproperty of semiconduction, and the source and the drain are connectedto each other by a portion of the body of the oxide semiconducting layerthat exhibits the predetermined original material property ofsemiconduction; and wherein the structure of the oxide thin filmtransistor further comprises a substrate, a gate on the substrate, agate isolated layer on the substrate and the gate, and a protectivelayer on the source and the drain, the oxide semiconducting layer beinglocated on the gate isolated layer.